Tanks or cylinders containing compressed gases are used in various applications including scuba diving, fire fighting and in various chemical environments. Large tanks weighing hundreds of pounds and more are typically handled using special material handling equipment. Small tanks such as residential fire extinguishers can be handled easily by a single person and need no additional equipment. In-between these sizes are a variety of tanks that are used in a number of different applications, such as compressed air scuba tanks, oxygen tanks used for hospital and home-based health care, and other such tanks in which the weight is greater than some nominal amount (e.g., over 15 pounds), but not too heavy that they cannot be handled by a single person using a hand truck (i.e., a caddy).
For scuba diving, transporting an air tank and dive equipment by hand can be difficult and even impossible for some divers to carry any distance. The weight of an air tank with dive gear can be as high as 80 lbs. For diving in remote areas, the divers have to transport their gear to and from the dive location, and the weight and difficulty of transporting the equipment can be an obstacle to diving in certain locations.
A standard caddy generally includes a base for receiving and supporting the tank, a vertical support frame having a handle and a pair of wheels connected with the support member at the base. The tank is placed on the base, often then secured in place using a strap, and then transported by tilting the caddy back until the base lifts off the ground and the full weight of the caddy and tank is placed on the wheels. Once the desired location has been reached by the user, the tank is removed from the caddy.
For scuba tanks, U.S. Pat. Nos. 5,393,080 to Ross and 6,565,103 to Wilson, and U.S. Published Patent Application No. 2004-0104550 to Do each disclose a scuba tank caddy or dolly that is designed to remain on the tank during a dive. The Do application is directed to a boot having fixed wheels integrated into the boot and the Ross patent discloses a dolly having side rails and a pair of fixed wheels. The Wilson patent discloses a scuba tank caddy having retractable wheels for facilitating usage of the caddy in water and storage of the caddy when not in use. Wilson states that the wheel retracting means can be an over-center cam lever, and the drawings from the Wilson patent indicate that the wheels are mounted on a straight axle such that the wheels and axle can undergo rectilinear translational motion between the lowered (in use) and upper (storage) positions.